Plasma display device and plasma display panel driving method

ABSTRACT

A plasma display panel (PDP) that has a T-shaped electronic structure or an electrode structure with adjacent parts of the scan electrode and the sustain electrode being broad, and parts coupled to the bus electrodes being narrow in a like manner to the T-shaped electrode structure is provided. The PDP has various discharge modes according to magnitudes of sustain discharge voltages. A frame is divided into a plurality of subfields with respective weights and is driven in the PDP. The subfields with low weights use low sustain discharge voltages to perform a discharge with a small quantity of emitting light, and the subfields with high weights use high sustain discharge voltages to perform a discharge with a big quantity of emitting light, thereby increasing representation performance of low gray scales.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korea PatentApplication No. 2003-74641 filed on Oct. 24, 2003 in the KoreanIntellectual Property Office, the entire content of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a plasma display device and a plasmadisplay panel (PDP) driving method.

(b) Description of the Related Art

A PDP is a flat display that uses plasma generated via a gas dischargeprocess to display characters or images. Depending on its size, the PDPcan include tens to millions of pixels that are provided thereon in amatrix format. According to the supplied driving voltage waveforms anddischarge cell structures, PDPs can be categorized into direct current(DC) PDPs and alternating current (AC) PDPs.

Since the DC PDPs have electrodes exposed in the discharge space, theyallow a current to flow in the discharge space while the voltage issupplied, and therefore they are problematic in that they requireresistors for current restriction. On the other hand, since the AC PDPshave electrodes covered by a dielectric layer, capacitances arenaturally formed to restrict the current, and the electrodes areprotected from ion shocks in the case of discharging. Accordingly, theAC PDPs have a longer lifespan than the DC PDPs.

FIG. 1 shows a perspective view of an AC PDP.

As shown in FIG. 1, scan electrodes 4 and sustain electrodes 5 aredisposed over a dielectric layer 2 and a protection film 3. The scanelectrodes 4 and the sustain electrodes 5 in pairs are formed inparallel and are under a first glass substrate 1. A plurality of addresselectrodes 8 covered with an insulation layer 7 are installed on asecond glass substrate 6. Barrier ribs 9 are formed on the insulationlayer 7, between the address electrodes 8, and in parallel with theaddress electrodes 8. Phosphors 10 are formed on the surface of theinsulation layer 7 and between the barrier ribs 9. The first and secondglass substrates 1 and 6 are provided facing each other with dischargespaces between them 1 and 6 so that the scan electrodes 4 and thesustain electrodes 5 can cross the address electrodes 8. A dischargespace 11 between an address electrode of the address electrodes 8 and acrossing part of a pair of the scan electrodes 4 and the sustainelectrodes 5 form a discharge cell 12, which is schematically indicated.

FIG. 2 shows a PDP electrode arrangement diagram.

As shown in FIG. 2, the PDP electrodes have an m×n matrix configuration.Address electrodes A1 to Am are arranged in a column direction, and scanelectrodes Y1 to Yn and sustain electrodes X1 to Xn are alternatelyarranged in a row direction. The discharge cell 12 shown in FIG. 2substantially corresponds to the discharge cell 12 shown in FIG. 1.

In general, a frame is divided into a plurality of subfields withrespective weights and is driven in an AC PDP. For example, 256 grayscales can be represented through combination of eight subfields withthe weights of 1, 2, 4, 8, 16, 32, 64, and 128. In this instance, eachsubfield includes a reset period, an address period, a sustain period,and an erase period in a temporal operation variation manner.

In the reset period, the states of the respective cells are reset inorder to smoothly address the cells. In the addressing period, the cellsthat are turned on and the cells that are not turned on in a panel areselected, and wall charges are accumulated to the cells that are turnedon (i.e., the addressed cells). In the sustain period, discharge isperformed in order to actually display pictures on the addressed cells.

Recently, because of high efficiency of the PDPs, a magnitude of aquantity of light displayed by a discharge, i.e. brightness, hasincreased. In the case of displaying the gray scale of 0, a low quantityof light generated in the reset period is provided. In the case ofdisplaying the gray scale of 1, a quantity of light generated in theaddress period and a quantity of light generated by sustain dischargepulses in the sustain period are provided in addition to the quantity oflight generated in the reset period. Since the difference of brightnessbetween the gray scales of 0 and 1 (i.e., a minimum unit of differencein brightness) is increased because of summation of the quantities oflight in the address period and the sustain period, performance of lowgray representation (e.g., representation having lower brightness) isrestricted and/or degraded.

SUMMARY OF THE INVENTION

An aspect of the present invention provides a plasma display device withexcellent performance of low gray representation, and a PDP drivingmethod to facilitate the same.

In another aspect of the present invention, a low sustain dischargevoltage is used in a subfield with a low weight.

In an exemplary embodiment according to the present invention, a plasmadisplay device includes a PDP having a first electrode and a secondelectrode forming a discharge cell and a driver for dividing a frameinto a plurality of subfields having respective weights, driving them,and alternately applying sustain discharge pulses to the first andsecond electrodes in a sustain period. The subfields are divided into atleast two groups. A first voltage of a first sustain discharge pulse ofa first subfield of the subfields belonging to a first group of the atleast two groups. The first group includes at least the subfield havingthe lowest weight in the sustain period. The first voltage is less thana second voltage of a second sustain discharge pulse of a secondsubfield belonging to a second group of the at least two groups in thesustain period.

The difference between the second voltage and the first voltage may begreater than 5V (volts).

The first electrode may include a first bus electrode provided in apredetermined direction and a first discharge electrode formed in thedischarge cell and coupled to the first bus electrode. The secondelectrode may include a second bus electrode provided in a predetermineddirection and a second discharge electrode formed in the discharge celland coupled to the second bus electrode. In addition, the plasma displaydevice may include a first region at which a discharge is spread at thefirst and second discharge electrodes by the first sustain dischargepulse of the first voltage. The first region may be narrower than asecond region at which a discharge is spread at the first and seconddischarge electrodes by the second sustain discharge pulse of the secondvoltage.

The first discharge electrode may include a third region formed withinthe discharge cell and a fourth region for coupling the third region andthe first bus electrode. The second discharge electrode may include afifth region formed within the discharge cell and a sixth region forcoupling the fifth region and the second bus electrode. In addition, thesecond region may include at least part of the fourth and sixth regions.

The first region may include at least part of the third and fifthregions, and the second region may further include the third and fifthregions.

The discharge mode by the sustain discharge pulse of the first voltagemay be different from the discharge mode by the sustain discharge pulseof the second voltage.

A width of the fourth region toward the direction of the first buselectrode may be narrower than a length of the third region toward thedirection of the first bus electrode.

The PDP further may include address electrodes arranged to cross thefirst and second bus electrodes.

In another exemplary embodiment according to the present invention, amethod for dividing a frame into a plurality of subfields and drivingthem in a PDP including first electrodes and second electrodes formingdischarge cells is provided. The PDP driving method includes selecting afirst discharge cell to be turned on from among the discharge cells in afirst subfield of the subfields, sustain-discharging the selected firstdischarge cell in the first subfield and selecting a second dischargecell to be turned on from among the discharge cells in a second subfieldof the subfields. The second subfield has a weight different from thatof the first subfield. In addition, the method includessustain-discharging the selected second discharge cell in the secondsubfield. In the present method, a discharge mode for generating asustain discharge in the first subfield is different from a dischargemode for generating a sustain discharge in the second subfield.

In still another exemplary embodiment according to the presentinvention, a plasma display device includes a PDP. The PDP has a firstelectrode and a second electrode forming a discharge cell. The displaydevice also includes a driver for dividing a frame into a plurality ofsubfields having respective weights, driving them, and alternatelyapplying sustain discharge pulses to the first and second electrodes ina sustain period. The first electrode includes a first bus electrodearranged in a predetermined direction, a first region formed within thedischarge cell, and a second region for coupling the first region andthe first bus electrode. The second electrode includes a second buselectrode arranged in a predetermined direction, a third region formedwithin the discharge cell, and a fourth region for coupling the thirdregion and the second bus electrode. A width of the second region towardthe direction of the first bus electrode being narrower than a length ofthe first region toward the direction of the first bus electrode, andthe voltage of the sustain discharge pulse in at least one subfield isdifferent from the voltage of the sustain discharge pulse in anothersubfield.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, together with the specification, illustrateexemplary embodiment(s) of the present invention, and, together with thedescription, serve to explain the principles of the present invention:

FIG. 1 shows a partial perspective view of an AC PDP;

FIG. 2 shows a PDP electrode arrangement diagram;

FIG. 3 shows a brief conceptual diagram of a plasma display deviceaccording to an exemplary embodiment of the present invention;

FIG. 4 shows a partial plane view of a PDP according to an exemplaryembodiment of the present invention; and

FIG. 5 shows brightness of sustain discharge pulses with respect tovoltages in the PDP of FIG. 4.

DETAILED DESCRIPTION

In the following detailed description, only certain exemplaryembodiment(s) of the present invention are shown and described, simplyby way of illustration. As those skilled in the art would realize, thedescribed embodiment may be modified in various different ways, allwithout departing from the spirit or scope of the present invention.Accordingly, the drawings and description are to be regarded asillustrative in nature, and not restrictive.

FIG. 3 shows a brief conceptual diagram of a plasma display deviceaccording to an exemplary embodiment of the present invention.

As shown in FIG. 3, the plasma display device includes a PDP 100, acontroller 200, an address driver 300, an X (or sustain) electrodedriver 400, and a Y (or scan) electrode driver 500. The X electrodedriver 400 and the Y electrode driver 500 are separately provided inFIG. 3, but they can also be combined into a single unit.

The PDP 100 includes a plurality of address electrodes 20 provided inthe vertical direction, and scan electrodes 30 and sustain electrodes 40provided in pairs in the horizontal direction. The address driver 300receives an address drive control signal from the controller 200, andapplies address signals for selecting discharge cells to be displayed tothe respective address electrodes 20. The Y and X electrode drivers 500and 400 respectively receive sustain control signals from the controller200, and input sustain discharge pulses to the scan electrodes 30 andthe sustain electrodes 40 to sustain the selected discharge cells. Inthis instance, the sustain discharge pulses represent waveformsalternately applied to the scan electrodes 30 and sustain electrodes 40during the sustain period, and a voltage of the sustain discharge pulserepresents a difference of between the voltages applied to the scanelectrodes 30 and the sustain electrodes 40. The controller 200 receivesexternal image signals, generates an address drive control signal and asustain discharge control signal, and applies them to the address driver300 and the Y and X electrode drivers 500 and 400.

The PDP 100 has two discharge modes according to a voltage of thesustain discharge pulse applied to one of the scan electrode and thesustain electrode during the sustain period. That is, the PDP 100performs a low brightness discharge when the voltage of the appliedsustain discharge pulse is low, and performs a high brightness dischargewhen the voltage of the applied sustain discharge pulse is high. A PDP(e.g., the above-noted PDP 100) will be described in detail withreference to FIGS. 4 and 5.

FIG. 4 shows a partial plan view of a PDP according to a first exemplaryembodiment of the present invention.

As shown in FIG. 4, the PDP includes a rear substrate (e.g., thesubstrate 6 of FIG. 1) and a front substrate (e.g., the substrate 1 ofFIG. 1) facing each other. A plurality of address electrodes 20′ arevertically (in the y direction in FIG. 4) formed on the rear substrate,and a plurality of scan electrodes 30′ and sustain electrodes 40′ arehorizontally (in the x direction in FIG. 4) formed on the frontsubstrate.

A plurality of barrier ribs 50 are formed in the space between the rearsubstrate and the front substrate, and are formed in parallel to theaddress electrodes 20′ between two adjacent address electrodes 20′. Aspace formed by two adjacent barrier ribs 50 and the adjacent scanelectrode 30′ and the sustain electrode 40′ forms discharge cells 60R,60G, and 60B.

The scan electrode 30′ and the sustain electrode 40′ respectivelyinclude transparent electrodes 31 and 41 for generating a discharge inthe discharge cells 60R, 60G, and 60B. The scan electrode 30 and thesustain electrode 40 are also respectively coupled to bus electrodes 32and 42 for compensating high resistance of the transparent electrodes 31and 41 and obtaining conductivity. In general, the transparentelectrodes 31 and 41 can be realized with indium tin oxide (ITO)electrodes, and the bus electrodes 32 and 42 can be realized withmetallic electrodes. The scope of the present invention, however, is notlimited to the types of electrodes. Instead, all or some of theelectrodes can be replaced by any suitable conductive and/orsemi-conductive electrodes as would be recognized by those skilled inthe art. The transparent electrodes 31 and 41 are protruded at the buselectrodes 32 and 42 into the discharge cells 60R, 60G, and 60B, facingeach other. Also, the transparent electrodes 31 and 41 comprisehorizontal units 31 a and 41 a provided in the horizontal direction, andvertical units 31 b and 41 b provided in the vertical direction tocouple the centers of the horizontal units 31 a and 41 a and the buselectrodes 32 and 42. That is, the transparent electrodes 31 and 41 haveT shapes which have long facing parts and narrow parts coupled to thebus electrodes 32 and 42.

As also shown in FIG. 4, black stripes 70 for improving the contrast canbe formed at regions where the adjacent scan electrodes 30′ and thesustain electrodes 40′ are formed outside the discharge cells 60R, 60G,and 60B.

The configuration of the PDP according to the first exemplary embodimentof the present invention has been described above, and dischargecharacteristics of the PDP will now be described.

A paper in the International Display Workshops (IDW '97), entitled“Improvement of contrast ratio in coplanar structured AC-plasma displaypanels by confined discharge near the electrode gap” by Kimio Amemiyaand Takashi Nishio discloses that the sustain discharge characteristicsare varied at a low voltage of Vsm near the minimum voltage for asustain discharge and at a high voltage near a discharge firing voltage.That is, when a high voltage is used as a voltage for a sustaindischarge in the sustain period, a discharge is generated at the gap ofthe transparent electrodes 31 and 41 of the scan electrode 30 and thesustain electrode 40, and it is spread toward the bus electrodes 32 and42 moving along the transparent electrodes 31 and 41. When a low voltageis used as a voltage for a sustain discharge, a discharge is generatedat the gap of the transparent electrodes 31 and 41 of the scan electrode30 and the sustain electrode 40, and it is not spread.

Another paper in the International Display Workshops (IDW '98), entitled“High luminous efficiency and high definition coplanar AC-PDP withT-shaped electrodes” by Kimio Amemiya, Toshihiro Komaki, and TakashiNishio discloses the above-described phenomena in the PDP with aT-shaped electrode structure as shown in FIG. 4. In detail, when a lowvoltage is used for the T-shaped electrode, the discharge is onlygenerated near the gap (31 a and 41 a of FIG. 4) of the transparentelectrodes 31 and 41, and when a high voltage is used, the discharge isspread following the transparent electrodes 31 and 41.

Accordingly, the light emitting brightness caused by a sustain dischargepulse is low when the discharge is generated at the gap of thetransparent electrodes 31 and 41 and does not spread, and the brightnessis high when the discharge is spread through the transparent electrodes31 and 41. FIG. 5 shows brightness of sustain discharge pulses withrespect to voltages in the PDP of FIG. 4.

As shown in FIG. 5, the brightness according to the discharge of the PDPis varied depending on the voltage of the sustain discharge pulses. Inparticular, when the voltage of the sustain discharge pulse is less than165V, a first discharge mode which has relatively low brightnesscharacteristic is formed, and when the voltage of the sustain dischargepulse is greater than 175V, a second discharge mode which has relativelyhigh brightness characteristic is formed. The brightness characteristicsof the first and second discharge modes are not greatly varied when thevoltage is changed. Also, the brightness is greatly varied at thevoltage of between the first and second discharge modes according tovoltage variation, and in particular, the brightness is greatly variedby 5V-voltage variations as shown in FIG. 5.

The brightness is changed according to the voltage of the sustaindischarge pulse in the PDP, and the T-shaped electrode structure of FIG.4 has a plurality of discharge modes which have different brightnesscharacteristics according to voltages. The above-described structure iswell exemplified in the electrode structure wherein adjacent parts ofthe scan electrode 30′ and the sustain electrode 40′ are broad, andparts coupled to the bus electrodes 32 and 42 are narrow in a likemanner of the T-shaped electrode structure of FIG. 4.

A method for increasing representation performance of low gray scales byusing characteristics of the PDP according to the first exemplaryembodiment of the present invention will now be described.

One frame is divided into a plurality of subfields SF1 to SFn and isthen driven, in the PDP according to the first exemplary embodiment ofthe present invention. The respective subfields SF1 to SFn have weightsW1 to Wn (where W1≦W2≦. . . ≦Wn), and the number of sustain dischargepulses during the sustain period of the respective subfields SF1 to SFnis determined by the weight. The gray scales are represented inproportion to summation of the weights of the subfields at which thesustain discharge is performed. For example, 256 gray scales arerepresented by dividing one frame into eight subfields SF1 to SF8, andestablishing the weights W1 to Wn of the subfields SF1 to SF8 as 1, 2,4, 8, 16, 32, 64, and 128.

The quantity of emitting light displayed by the subfield SF1 with thelowest weight has been increased because of high efficiency of the PDP.Therefore, the voltage of the sustain discharge pulse of the subfieldSF1 with the lowest weight is established to be a voltage forrepresenting the brightness of the first discharge mode, and thevoltages of the sustain discharge pulses of the residual subfields SF2to SF8 are established to be voltages for representing the brightness ofthe second discharge mode. As a result, the brightness difference ofbetween the gray scales of 0 and 1 is reduced since the quantity oflight during the sustain period is reduced when representing the gray of0.

The voltage of the sustain discharge pulse of the subfield SF1 with thelowest weight is established to be a voltage for representing thebrightness of the first discharge mode in the first exemplaryembodiment, and in addition, the voltages of the sustain dischargepulses of a predetermined number of subfields SF1 and SF2 with lowweights can be established to be voltages for representing thebrightness of the first discharge mode. That is, a predetermined numberof subfields with low weights are defined to be a group, other subfieldsare defined to be another group, and sustain voltages of the groups areestablished to be different. Accordingly, representation performance inthe low gray scales becomes better because of the brightness differencebetween the grays of 1 and 2 compared to the first exemplary embodiment.When the voltages of the sustain discharge pulses of all the subfieldsare established as the above-noted voltage, the overall brightness isreduced, and an appropriate number of subfields can be selectedaccording to the representation performance of low gray scales requiredby panel characteristics.

The sustain discharge is performed on the subfield with low weights inthe first discharge mode of FIG. 5, and the sustain discharge isperformed on the subfield with high weights in the second discharge modeof FIG. 5, and differing from this, another discharge mode is possible.That is, a sustain discharge may be performed on the subfield with a lowweight in the discharge mode of between the first and second dischargemodes. Hence, the brightness difference of between the grays of 0 and 1is increased compared to the first exemplary embodiment, but the abovemethod can be applicable to a panel which requires representationperformance of a low gray scale lower than the first exemplaryembodiment. For example, when the voltage of the sustain discharge pulseof the subfield SF1 is established to be 170V, and the voltages of thesustain discharge pulses of the subfields SF2 to SFn are established tobe 175V, the representation performance of a low gray scale is increasedsince the brightness difference caused by the sustain discharge pulsebecomes manifest as shown in FIG. 5.

Also, the PDP having the T-shaped electrode structure has been describedin the first exemplary embodiment. However, the present invention is notlimited to the first exemplary embodiment, and can be applied to all theelectrode structures which substantially have the above-describeddischarge modes of the T-shaped electrode structure shown in FIG. 4. Oneexample thereof is an electrode structure in which a region wheretransparent electrodes of the scan electrode and the sustain electrodeis broad and a region coupled to the bus electrode is narrow.

As described, the characteristics of different discharge modes accordingto voltages of the sustain discharge pulses in the PDP are used, inwhich a low sustain discharge voltage is used in the low subfield and ahigh sustain discharge voltage is used in the high subfield, andaccordingly, the representation performance of low gray scales isenhanced.

While this invention has been described in connection with certainexemplary embodiment(s), it is to be understood that the invention isnot limited to the disclosed embodiment(s), but, on the contrary, isintended to cover various modifications included within the spirit andscope of the appended claims and equivalents thereof.

1. A plasma display device comprising: a plasma display panel includinga first electrode and a second electrode forming a discharge cell; adriver for dividing a frame into a plurality of subfields havingrespective weights, driving the plurality of subfields, and alternatelyapplying sustain discharge pulses to the first and second electrodes ina sustain period, wherein the subfields are divided into at least twogroups; and a first voltage of a first sustain discharge pulse of afirst subfield of the subfields belonging to a first group of the atleast two groups, the first group including at least the subfield havingthe lowest weight in the sustain period, wherein the first voltage isless than a second voltage of a second sustain discharge pulse of asecond subfield belonging to a second group of the at least two groupsin the sustain period.
 2. The plasma display device of claim 1, whereinthe difference between the second voltage and the first voltage isgreater than 5V (volts).
 3. The plasma display device of claim 1,wherein the first electrode comprises a first bus electrode provided ina predetermined direction and a first discharge electrode formed in thedischarge cell and coupled to the first bus electrode, the secondelectrode comprises a second bus electrode provided in a predetermineddirection and a second discharge electrode formed in the discharge celland coupled to the second bus electrode, and a first region at which adischarge is spread at the first and second discharge electrodes by thefirst sustain discharge pulse of the first voltage is narrower than asecond region at which a discharge is spread at the first and seconddischarge electrodes by the second sustain discharge pulse of the secondvoltage.
 4. The plasma display device of claim 3, wherein the firstdischarge electrode includes a third region formed within the dischargecell and a fourth region for coupling the third region and the first buselectrode, the second discharge electrode includes a fifth region formedwithin the discharge cell and a sixth region for coupling the fifthregion and the second bus electrode, and the second region includes atleast part of the fourth and sixth regions.
 5. The plasma display deviceof claim 4, wherein the first region includes at least part of the thirdand fifth regions and wherein the second region further includes thethird and fifth regions.
 6. The plasma display device of claim 4,wherein a width of the fourth region toward the direction of the firstbus electrode is narrower than a length of the third region toward thedirection of the first bus electrode.
 7. The plasma display device ofclaim 3, wherein the plasma display panel further comprises addresselectrodes arranged to cross the first and second bus electrodes.
 8. Theplasma display device of claim 1, wherein the discharge mode by thefirst sustain discharge pulse of the first voltage is different from thedischarge mode by the second sustain discharge pulse of the secondvoltage.
 9. A method for dividing a frame into a plurality of subfieldsand driving the plurality of subfields in a plasma display panelincluding first electrodes and second electrodes forming dischargecells, the method comprising: selecting a first discharge cell to beturned on from among the discharge cells in a first subfield of theplurality of subfields; sustain-discharging the selected discharge cellin the first subfield; selecting a second discharge cell to be turned onfrom among the discharge cells in a second subfield of the plurality ofsubfields, wherein the second subfield has a weight different from thatof the first subfield; and sustain-discharging the selected seconddischarge cell in the second subfield, wherein a discharge mode forgenerating a sustain discharge in the first subfield is different from adischarge mode for generating a sustain discharge in the secondsubfield.
 10. The method of claim 9, wherein a first voltage forsustain-discharging the first discharge cell in the first subfield isless than a second voltage for sustain-discharging the second dischargecell in the second subfield.
 11. The method of claim 10, wherein thedifference between the first voltage and the second voltage is greaterthan 5V (volts).
 12. The method of claim 9, wherein the first electrodecomprises a first bus electrode arranged in a predetermined direction, afirst region formed within the discharge cell, and a second region forcoupling the first region and the first bus electrode, and the secondelectrode comprises a second bus electrode arranged in a predetermineddirection, a third region formed within the discharge cell, and a fourthregion for coupling the third region and the second bus electrode. 13.The method of claim 12, wherein a width of the second region toward thedirection of the first bus electrode is narrower than a length of thefirst region toward the direction of the first bus electrode.
 14. Aplasma display device comprising: a plasma display panel including afirst electrode and a second electrode forming a discharge cell; and adriver for dividing a frame into a plurality of subfields havingrespective weights, driving the plurality of subfields, and alternatelyapplying sustain discharge pulses to the first and second electrodes ina sustain period, wherein the first electrode comprises a first buselectrode arranged in a predetermined direction, a first region formedwithin the discharge cell, and a second region for coupling the firstregion and the first bus electrode, wherein the second electrodecomprises a second bus electrode arranged in a predetermined direction,a third region formed within the discharge cell, and a fourth region forcoupling the third region and the second bus electrode, wherein a widthof the second region toward the direction of the first bus electrode isnarrower than a length of the first region toward the direction of thefirst bus electrode, and wherein the voltage of the sustain dischargepulse in at least one subfield is different from the voltage of thesustain discharge pulse in another subfield.
 15. The plasma displaydevice of claim 14, wherein the at least one subfield is a subfield witha low weight.